Most yo-yos are in the form of two disk-shaped side units that are rigidly connected to each other, in a spaced-apart relation, by some form of axle structure. The side units may be of a unitary or multi-part construction and are usually made out of plastic, wood and/or metal. The axle structure typically extends through the center of both side units and can be an assembly of multiple parts, or be a single part structure, such as a wooden dowel. To reduce friction, many modern yo-yos employ an axle structure that includes a center-located rotatable member as the point of attachment for the yo-yo's tether.
A yo-yo tether is commonly in the form of a long string that is made from a plurality of cotton strands that are twisted together. To enable the securement of the tether to the axle structure, one end of the tether is adapted to create a loop that is positioned to encircle a center portion of the axle structure. The other end of the tether is usually tied to create a second loop that can be placed about one of a user's fingers to thereby secure the tether, and effectively the yo-yo, to the user's hand.
When the tether is wound about the axle structure and the yo-yo is then released, or thrown, from the user's hand, the yo-yo will begin to rapidly spin as it moves away from the user's hand. This occurs as a result of the tether unwinding from about the axle structure. When the tether fully unwinds from about the axle structure, the yo-yo may “sleep” at the end of the tether, whereby the yo-yo's side units continue to spin without the tether rewinding on the axle structure. Once the yo-yo is sleeping, there are a number of tricks, such as “walk the dog,” that a person can perform with the spinning yo-yo. A sleeping yo-yo is also often used to perform “string tricks” that involve temporarily placing the spinning yo-yo onto a portion of the tether intermediate of the tether's two ends.
Normally, at the finish of a yo-yo trick, the user of the yo-yo will make a quick jerk on the tether in order to have the yo-yo return to the user's hand. By jerking on the tether, the user causes a brief tightening of the tether, which is then automatically followed by a temporary slackening of the tether. Once the tether goes slack, the tether's twist will cause one or more portions of the tether located proximate the axle structure to move to the side, and thereby engage, a spinning portion of the yo-yo. Once an engagement has occurred, the tether portion can become locked to a spinning portion of the yo-yo. A locking engagement is usually due to the tether becoming snagged on a surface of the spinning portion, or to a bunching of the tether against said spinning portion. Once a locking engagement has occurred, further rotation of the spinning portion of the yo-yo winds the tether about the axle structure, thereby causing the yo-yo to return to the user's hand.
Every yo-yo has three crucial performance characteristics that determine its ability to perform tricks. They are the yo-yo's potential sleep time, its smoothness on the tether, and its ability to return on command.
Concerning a yo-yo's sleep time, the longer the yo-yo can be made to sleep, the more time a user will have to complete any particular yo-yo trick. It is well known that by minimizing friction in the yo-yo's components, one can maximize the yo-yo's sleep time. Furthermore, it is known that whenever the tether even slightly rubs against a spinning portion of the yo-yo, the created friction will reduce the yo-yo's sleep time.
Concerning a yo-yo's ability to be smooth on the tether, this refers to a yo-yo's ability, when it is sleeping at the end of the tether, to be temporarily placed on a medial portion of the tether without inadvertently returning to the user's hand. An example of a trick that requires a yo-yo to be smooth on the tether is “man on the trapeze.” If, during such a trick, the spinning yo-yo can slide on the tether, the yo-yo is said to be very smooth on the tether.
The ability of a yo-yo to return on command is the primary measure of a yo-yo's responsiveness. Return on command refers to the ability of the yo-yo to return to the user's hand after the yo-yo is commanded to return via a quick jerk on the yo-yo's tether. The structure and design of the yo-yo must be such that when the tether briefly goes slack, a portion of the tether can move to the side and create a locking engagement with a spinning portion of the yo-yo. In most prior art yo-yos, the ability of the tether to become lockingly engaged to a spinning portion of the yo-yo is enhanced through the use of tether engagement adaptations located in, or on, the tether-facing surface of the yo-yo'side units. Examples of tether engagement adaptations known in the art include an array of raised ribs, indentations, and/or rubber pads. The tether-facing surface of a side unit is herein defined as the surface of the side unit that faces a portion of the yo-yo's tether when said tether extends straight out from the yo-yo's string gap. A yo-yo's string gap is herein defined as the area located between the yo-yo's side units.
While tether engagement adaptations, such as raised ribs, enhance a yo-yo's ability to return on command, they can adversely affect a yo-yo's sleep time and smoothness on the tether. For example, engagement adaptations that extend deeply into the string gap will usually cause an increase in the frequency of inadvertent contacts between the tether and the adaptations. An increase in inadvertent contacts will increase both friction and the likelihood of an inadvertent return of the spinning yo-yo when it is placed on a medial portion of the tether. The large number of different tether engagement adaptations found in the prior art reflect an effort by inventors to create yo-yos that are either specially adapted for the performance of certain types of yo-yo tricks, or that provide a unique compromise of yo-yo performance characteristics.
Watson (U.S. Pat. No. 6,331,132) teaches a yo-yo in which each side unit has a tether engagement adaptation in the form of a flat, ring-shaped pad of fibrous material. In the taught yo-yo, replacement of a worn pad can be onerous since the glue used to secure the pad can leave a residue on the side unit's tether-facing surface when the pad is removed. In addition, the pads provide no means for changing the yo-yo's responsiveness.
Van Dan Elzen et al (U.S. Pat. No. 5,813,898) teaches a different form of tether engagement adaptation. Spaced-apart pads of a relatively high-friction material are affixed to the tether-facing surface of each side unit. The pads provide no means for adjusting the yo-yo's responsiveness, and their removal can leave a glue residue on the tether-facing surface of each of the yo-yo's side units.
Most prior art yo-yos lack tether engagement adaptations that can be easily and quickly replaced once they become worn. In addition, prior art yo-yos usually also lack replaceable tether engagement members that are firmly secured to-the associated yo-yo side unit without the use of an adhesive. Completely unknown in the prior art is a yo-yo in which the tether engagement adaptations can be replaced without requiring special replacement parts. Furthermore, prior art yo-yos lack adjustable tether engagement adaptations that can maximize the yo-yo's responsiveness and smoothness on the tether while minimizing the tendency for the yo-yo to inadvertently return to the user. As a result, there is a need for a yo-yo that has unique performance characteristics via replaceable, adjustable tether engagement adaptations that enable the yo-yo to be usable for all types of yo-yo tricks and by yo-yo players of all skill levels.